Use of catheters to administer fluids into and drain fluids out of the body has been a standard practice in medical procedures for years. Many such catheters are available and used as part of an extracorporeal circuit during open heart procedures.
In a typical open heart procedure, blood is bypassed from the heart and lungs to a heart lung machine which, in combination with an oxygenator, pumps and oxygenates the blood passing through the extracorporeal circuit. When bypassing the heart, blood is siphoned away from the right atrium using a venous return (suction) catheter, oxygenated and returned to the aorta using an aortic arch (delivery) catheter. The distal end of the venous return catheter is usually placed in the right atrial appendage, while the proximal end of the catheter is attached to the tube feeding to a venous reservoir. The venous reservoir is placed at a lower level than the operating table to create a differential head pressure. This differential head pressure acts to siphon blood residing in the right atrium via the venous return catheter into the venous return reservoir.
During the open heart procedure, both the venous return catheter and aortic arch catheter are first introduced into the heart, and specifically the right atrium and inferior vena cava of the heart, and the aorta, respectively. The catheters are then clamped to inhibit blood flow therethrough. When the patient is ready to be placed on the extracorporeal circuit, the catheters are connected to inlet and outlet ends of the extracorporeal circuit, respectively, while simultaneously releasing the clamps.
Periodically, during the open heart procedure, the heart needs to be moved or adjusted by the surgeon. As the suction catheter and delivery catheter are already attached to the heart, there is a potential for these catheters to bend and kink, which can restrict blood flow therethrough and possibly create a dangerous and even life threatening situation. One prior art catheter which tends to avoid kinking is disclosed in U.S. Pat. No. 4,129,129 to Sarns. This catheter has an extremely thick tube body with a coil imbedded in the tube walls. Reinforcing the tube wall, however, significantly increases the outer diameter of the catheter. As such, the larger outer diameter requires a larger incision to be formed in the heart for introducing this large catheter, which tends to cause more trauma to the heart. Another disadvantage with this prior art catheter is that it can only be clamped in the non-reinforced area of the catheter which is provided at the proximal end of the catheter. This unreinforced section is in an inconvenient location for the surgeon, and restricts the surgeon from choosing the location of the clamp during the surgery.
There are three main areas of concern when performing the surgery in the conventional way. First, the kinking of the venous line, such as at the catheter tip, could potentially run the venous reservoir dry and allow air into the patient's circulation system. This introduction of air would be fatal. Secondly, the trauma on the heart created by a larger incision takes longer to heal and creates a larger scar. Finally, it is inconvenient for the surgeon to clamp only at the selected areas of the catheter.
There is a desire to provide a reinforced catheter that has a high inner to outer diameter ratio, a sufficient inner diameter and a small outer diameter which facilitates for smaller incision in the right atrium.